The invention relates to a mechanical switching contact for double pole or bipolar switchover, especially under-load switchover, of a tap changer or step switch, especially for a tapped transformer.
A switchover arrangement for the switchover under load of a tap changer is known from WO 95/24724 (U.S. Pat. No. 5,786,552), which has a mechanical main switching contact and an also mechanical resistance switching contact. Both the main switch contact and also the resistance switching contact are comprised of two mutually interconnected actuatable individual interrupter contacts whereby each individual interrupter contact of the main switching contact and also of the resistance switching contact is electrically connected with the first load switching side and the respective other individual interrupter contact of both the main switching contact and also of the resistance switching contact are electrically connected with the second load switchover side. With this arrangement, the individual interrupter contacts of the main switching contact are switchable through a first changeover switch and the individual interrupter contacts of the resistance switching contact are switchable through a second changeover switch. There is thus a respective double-pole switchover by means of two changeover contacts.
From WO 96/309222 (U.S. Pat. No. 5,834,717) an under-load switchover for a tap changer [step switch] is known which technologically is proposed in the form of a double-pole switch having mechanical contacts pivotable in a lever-like manner about a pivot point. In addition, spring-loaded toggle levers are provided which act upon the rotatably mounted mechanical contacts in such manner that these can assume two switching positions on either side of a dead point. The two movable contacts are arranged in the same horizontal plane at the outer region of the load switch for each phase.
This known configuration of the mechanical switching contacts for double-pole interruption is however complex and technologically expensive, requires precise adjustment after mounting and needs for that purpose a relatively large amount of space.
It is the object of the invention therefore to provide a mechanical switch contact for a double pole or bipolar switchover which is of simple construction and has the smallest possible number of parts to facilitate mounting and therefore has a modular configuration so that it is composed of a self-standing component which can be built into a device for switching over under load without further adjustment or matching efforts and in addition will occupy the smallest possible space.
This object is achieved with a mechanical switching contact for double-pole switchover, especially for an under-load switchover, of a tap changer, with the following features:
it has an insulating carrier or support on which fixed contacts are arranged pairwise and opposite one another;
on the insulating carrier a contact carrier is rotatably mounted which has on one of its two free ends a pivot arm and which has an actuating contour on its other free end;
on the pivot arm an electrically conducting contact piece is so arranged that depending upon the respective possible end position of the contact carrier in a stationary state conductively connects two of the fixed contacts which are arranged pairwise adjacent one another on one of the two sides; and
on both sides of the pivot arm telescoping guides each with a respective compression spring are provided which respectively have one of their free ends braced against the contact carrier and with the other free end braced against the insulating carrier such that the contact carrier has a snap effect and by application of force to the actuating contour is swingable to jump from one stationary state into another stationary state.
The telescoping guides with respective compression springs-are braced each at one on their free ends on an abutment receiver on the contact carrier and with the respective other free end on a cup receiver on the insulating carrier such that a three-dimensional spatial mounting at the bracing points is produced.
The insulating longitudinal guides are such that at least two identical mechanical switch contacts are modularly connectable with one another.
The contact piece in the middle region in a contact receiver of the pivot arm has on its two free ends each a respective contact roller each of which cooperates with a respective one of the fixed contacts.
The important advantage of the mechanical switching contact of the invention resides in its extraordinarily compact and simple construction. With fewer parts it allows both the mechanical main switching contact as well as the mechanical resistance switching contact to be prefabricated as identical modular components. For the main switching contact as well as for the resistance switching contact the same modular mechanical switching contacts are useable.
The main switch contact and resistance switching contact of each phase can be realized in a simple manner as common components of two identical, mutually connected modular switch contacts according to the invention.